World's largest cave to be preserved in its natural state

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In a move that will delight conservationists, the government has banned any construction work at Phong Nha-Ke Bang cave system.

This is where Son Doong was discovered at 490ft below the ground in 1991. You could, if you wanted to, fit a Boeing 747 through its biggest cavern. Cavers who swing down to its depths (it has been open to the public since 2013 but licences to enter are very few) discover subterranean forests, 350-million-year old coral fossils, and an underground lake.

The 300 caves and grottos here, which were recognised as a Unesco heritage site in 2003, will now apparently remain undisturbed, much as they have been for 400 million years.

A plan to build an 11km cable car system above Son Doong received widespread opposition last October, according to thanhniennews.com. After conservationists and tourists condemned the plans, Nguyen Huu Hoai, the local mayor, committed instead to not building roads or shelters in the caves while keeping the tourist operation small and limited to the 5km Son Doong cave that is already open.

Credit: John Spies/Barcroft Media

Australian photographer John Spies, 59, spent a week photographing the natural wonder of the cave system. "With ceilings towering over 200 metres high in places, the cave is a humbling and belittling experience," he said.

“Visitors must descend 80m down a steep wall with the use of harnesses and ropes. The huge temperature difference creates moving clouds of mist, especially near the two karst windows, which gives the cave its magically surreal atmosphere."

“Phong Nha-Ke Bang National Park is riddled with an astonishing number of cave systems,” he wrote, “including the Hang Son Doong (the world’s largest cave) the scenery is spectacular with rainforest, towering karst peaks and jungle rivers.

“In the last couple of years, accommodation choices have mushroomed to meet demand, including the Lake House Resort (phongnhalakehouse.com), though there’s still only one ATM in the one-horse access town.”

Local tour operator Oxalis (oxalis.com.vn/tour/son-doong-cave-expedition), co-run by British cavers, offers superb trips to the sublime swim-through caverns of Tu Lan and Hang En (the world’s third largest cave). It also offers tours to Son Doong for a lucky few but they are currently booked up.